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DNxHD no recompression

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Grzegorz Kwiatkowski
DNxHD no recompression
on May 5, 2012 at 5:49:37 am

I am delivering big (20GB) episodes in DNxHD and sometimes I got to do small corrections. It is extremely annoying to render the whole project once again only to change a few frames or audio.

Is there any way to correct certain parts of video without recompressing the whole video? If not AVID, maybe some other software can handle it?


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Mike Most
Re: DNxHD no recompression
on May 5, 2012 at 4:31:54 pm

That's why most high end users work with and render to image sequences (DPX and the like). With an image sequence, each frame is its own file and can be individually replaced. This is not possible with wrapped movie formats like Quicktime and MXF. Unfortunately, Media Composer does not currently support image sequences for output. You would have to use either Avid DS, Autodesk Smoke, or perhaps Assimilate Scratch or Premiere Pro for that kind of support.


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Michael Phillips
Re: DNxHD no recompression
on May 5, 2012 at 5:18:51 pm

It does support image sequences, but only as TIF, JPEG, etc. and not DPX, etc. So depending on your needs, it may, or may not work.

Michael

Michael Phillips


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Grzegorz Kwiatkowski
Re: DNxHD no recompression
on May 5, 2012 at 6:44:04 pm

When I worked with mpeg2 I used Womble. Great software that allows to edit particular frames or swap audio without recompression. Now, I work with DNxHD and the things ain't so easy.


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Shane Ross
Re: DNxHD no recompression
on May 5, 2012 at 11:26:17 pm

Yeah...that's the big issue with Quicktime deliverables. No way to do an INSERT EDIT. Trust me, I've tried many ways, and all have failed.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Grzegorz Kwiatkowski
Re: DNxHD no recompression
on May 6, 2012 at 5:40:49 am

have you tried Avisynth and ffmpeg?


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Grzegorz Kwiatkowski
Re: DNxHD no recompression
on May 6, 2012 at 4:58:14 pm

ok, insert edit doesn't work but my life would be way easier if I could at least mux video stream with audio or swap audio in DNxHD file. Have u tried this?


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Eugeny Korkhin
Re: DNxHD no recompression
on May 12, 2012 at 11:00:26 am

[Grzegorz Kwiatkowski] "ok, insert edit doesn't work but my life would be way easier if I could at least mux video stream with audio or swap audio in DNxHD file. Have u tried this?"

It's hard to advice here as you want to swap audio in something you call "DNxHD file", when DNxHD is a codec, not a container. But if you have DNxHD stream and audio wrapped into a "mov" file, then replacing audio is not a big deal. With no recompression, only re-wrap. Insert edits, by the way, also work. All you need is a Quicktime player (not X, of course, but a Pro version of QuickTime 7).

Let's say you have a master file "File 1" which consists of video stream "v1" and audio stream "a1". And you have a new audio file "Audio file" which consists of audio stream "a2" only. Open the "File 1" with Quicktime player, cmd+j, select "a1" audio stream, press delete. Now open "Audio file" with QuickTime player, cmd+a, cmd+c, switch back to the "File 1", place the playhead at the beginning, cmd+alt+v. That's it. Now you need to save it as a new self-contained moive: cmd+shift+s, enter the name, choose the destination and save. It takes time, comparable to the time of copying the file.

Insert edits are almost the same, but require more accuracy. First, render the corrected part of the movie as a separate "File 2". Let's say, it is 20 frames long. Open it with QuickTime, cmd+a, cmd+c. Open the "File 1", place the playhead at the point where your insert should start, mark IN (i on the keyboard), place the playhead at the point where the insert ends and mark OUT (o)(it is very important to mark the exact duration you are going to insert (20 frames in our case). Otherwise it will be "Fit-to-fill"), cmd+alt+shift+v. That's it. Now you need to save it as a new self-contained moive: cmd+shift+s, enter the name, choose the destination and save. It takes time, comparable to the time of copying the file ))

Hope that helps.


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Eugeny Korkhin
Re: DNxHD no recompression
on May 12, 2012 at 4:16:07 pm

Correcting myself:
When doing video insert, no need to cmd+alt+shift+v. cmd+alt+v is quite enough)) Just mark IN. OUT seems to be unnecessary. And thus forget about Fit-to fill.


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Grzegorz Kwiatkowski
Re: DNxHD no recompression
on May 13, 2012 at 11:04:01 am

Eugeny,

if it works, you just saved hours of my life :-).


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Eugeny Korkhin
Re: DNxHD no recompression
on May 13, 2012 at 3:44:39 pm

There's certainly a better way to spend those hours))
Just to remind: it is not lightning fast. It's not like you press cmd+s and ready to go. No. It's more like taking a 20gig file and duplicating it.
I'm really interested if it works for you or not. Post the results, please.


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Grzegorz Kwiatkowski
Re: DNxHD no recompression
on May 14, 2012 at 11:33:55 am

Eugeny,

it seems to work! What should I choose to save the file? Save as or export? I don't want to recompress the video.


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Eugeny Korkhin
Re: DNxHD no recompression
on May 14, 2012 at 11:44:52 am

Grzegorz,
You should choose "Save as..." and save file as self-contained movie. Thus you'll get a flattened file.
Exporting = recompress.


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